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Virus classification
Group: Group II (ssDNA)
Order: Unassigned
Family: Circoviridae

The Circoviridae are a family of viruses. These are small, relatively poorly studied viruses, with circular, single-stranded DNA genomes of approximately one to four kilobases.


Circoviridae virons are non enveloped and about 20 nanometers in diameter with icosahedral symmetry (triangulation number (T) = 1). The capsid consists of 12 pentagonal trumpet shaped pentamers.

The genome is monopartite, circular, single-stranded DNA of between 1.8 to 3.8 kilobases. There are two main open reading frames arranged in opposite directions that encode the replication (Rep) and capsid (Cap) proteins. Alternative start codons are common in the avian species.

The viruses replicate their genomes via a rolling circle mechanism. A stem loop structure with a conserved nonanucleotide motif is located at the 5' intergenic region of circovirus genomes and is thought to initiate rolling-cycle replication.


The family Circoviridae contains three genera, Circovirus, Cyclovirus and Gyrovirus.

Two circoviruses have been identified in fish—Barbel circovirus (BaCV) 1 and 2.[1] Their genomes are in length and contain two major open reading frames similar to the capsid and replication associated protein genes found in other circoviruses.

  • Genus Cyclovirus : Dragonfly cyclovirus, Florida woods cockroach-associated cyclovirus[3]


A cyclovirus—cyclovirus-Vietnam—has been isolated from the cerebrospinal fluid of 25 Vietnamese patients with CNS infections of unknown aetiology.[4] The same virus has been isolated from the faeces of healthy children and also from pigs and chickens. This suggests an orofaecal route of transmission with a possible animal reservoir.

See also[edit]


  1. ^ Lorincz M, Csagola A, Farkas SL, Szekely C, Tuboly T (2011) First detection and analysis of a fish circovirus. J Gen Virol
  2. ^ Mankertz P (2008). "Molecular Biology of Porcine Circoviruses". Animal Viruses: Molecular Biology. Caister Academic Press. ISBN 978-1-904455-22-6. 
  3. ^ Dayaram A, Potter KA, Moline AB, Rosenstein DD, Marinov M, Thomas JE, Beitbart M, Rosario K, Argüello-Astorga GR, Varsani A (2013) High global diversity of cycloviruses amongst dragonflies. J Gen Virol
  4. ^ Tan le V, van Doorn HR, Nghia HD, Chau TT, Tu le TP, de Vries M, Canuti M, Deijs M, Jebbink MF, Baker S, Bryant JE, Tham NT, Bkrong NT, Boni MF, Loi TQ, Phuong le T, Verhoeven JT, Crusat M, Jeeninga RE, Schultsz C, Chau NV, Hien TT, van der Hoek L, Farrar J, de Jong MD (2013) Identification of a new cyclovirus in cerebrospinal fluid of patients with acute central nervous system infections. MBio 4(3). pii: e00231–13. doi: 10.1128/mBio.00231-13

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